After a wellbore is drilled, a casing string is lowered into the wellbore. While running the casing string in the wellbore, it is often the practice to cause the well fluid to sustain a portion of the weight of the casing string by floating the casing string in the well fluid. Typically, plugs (or packers) are installed inside the casing string to isolate a portion of the casing string. The isolated portion of the casing string may be filed with a low-density fluid or air to create a buoyant force when the casing string is lowered into the wellbore. The plugs (or packers) are eventually removed from the casing string by a costly drilling operation. Therefore, there is a need for a casing float sub that may be selectively removed from the casing string without the need of a drilling operation.